I live at 668m and my gf lives at 2240m so I´ve brewed tea at very different altitudes!

At high altitude you just can´t get the water as hot as at lower altitude...but you can make sure to pour the water from the kettle right away once it reaches a full boil and pour close to the pot to prevent heat loss. Also I find with teas that require boiling water they need to be steeped a little but longer at altitude than closer to sea level.

Even that tea still tastes different at high altitude but you can still get good results from your blacks, puerhs and oolongs.